Hydroxylation

Source: Wikipedia, the free encyclopedia.
Hydroxylation and hydroxylases are not to be confused with hydrolysis and hydrolases.

In chemistry, hydroxylation can refer to:

Hydroxylation reactions

Synthetic hydroxylations

Installing hydroxyl groups into organic compounds can be effected by various metal catalysts. Many such catalysts are biomimetic, i.e. they are inspired by or intended to mimic enzymes such as cytochrome P450.[2]

Whereas many hydroxylations insert O atoms into

Sharpless dihydroxylation is such a reaction: it converts alkenes into diols. The hydroxy groups are provided by hydrogen peroxide, which adds across the double bond of alkenes.[3]

Biological hydroxylation

In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. A C−H bond is converted to an alcohol by insertion of an oxygen atom into a C−H bond. Typical stoichiometries for the hydroxylation of a generic hydrocarbon are these:

Since O2 itself is a slow and unselective hydroxylating agent, catalysts are required to accelerate the pace of the process and to introduce selectivity.[4]

Hydroxylation is often the first step in the degradation of organic compounds in air. Hydroxylation is important in

drugs (for example, steroids) are activated or deactivated by hydroxylation.[5]

The principal hydroxylation agent in nature is

cytochrome P-450, hundreds of variations of which are known. Other hydroxylating agents include flavins, alpha-ketoglutarate-dependent hydroxylases (2-oxoglutarate-dependent dioxygenases), and some diiron hydroxylases.[6]

Steps in an oxygen rebound mechanism that explains many iron-catalyzed hydroxylations: H-atom abstraction, oxygen rebound, alcohol decomplexation.[4]

Of proteins

The hydroxylation of proteins occurs as a

hypoxia inducible factors. In some cases, proline may be hydroxylated instead on its β-C atom. Lysine may also be hydroxylated on its δ-C atom, forming hydroxylysine (Hyl).[10]

These three reactions are catalyzed by very large, multi-subunit enzymes

limeys".[11]

Several endogenous proteins contain hydroxyphenylalanine and hydroxytyrosine residues. These residues are formed due to the hydroxylation of phenylalanine and tyrosine, a process in which the hydroxylation converts phenylalanine residues into tyrosine residues. This is very important in living organisms to help them control excess amounts of phenylalanine residues.[8] Hydroxylation of tyrosine residues is also very vital in living organisms because hydroxylation at C-3 of tyrosine creates 3,4- dihydroxy phenylalanine (DOPA), which is a precursor to hormones and can be converted into dopamine.

Examples

References

  1. PMID 11121513
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  2. PMID 11513570
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  3. doi:10.1021/cr00032a009
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  4. ^
    PMID 27909920
    .
  5. S2CID 25516145
    .
  6. ISBN 1-57259-153-6.[page needed
    ]
  7. PMID 27663420
    .
  8. ^
    S2CID 243626930
  9. PMID 10021421
    .
  10. S2CID 85784668
    .
  11. ISBN 978-1-119-45166-2
    .
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